The auto industry has work ahead to meet ambitious fuel efficiency goals of 55 miles per gallon by 2025 — nearly twice the current average required. Hybrid and electric cars will play a role, but the plain old internal combustion engine can't be overlooked.

To find out where the new technology is being developed to make more gas engines more efficient, I went on a tour of an engine lab with professor Anna Stefanopoulou, director of the Automotive Research Center at the University of Michigan. I was expecting cams and pistons, but she first showed me computers screens.

"It's hard to see, since a lot of the work we do is not necessarily only hardware [but] software," Stefanopoulou says. "If you really need to meet the [55 mpg standard] and to do it cost-effectively, you have to do it sometimes through strategy."

Eventually Stefanopoulou and I wound up looking at one of the dozen engines that they test here. She says they test it once a week, sometimes once a day.

"We don't run durability tests here: We run tests to model the engine and then be able to understand what's going on with running different fuels," she says.

This particular engine can run on a variety of fuels, and Stefanopoulou and her students are working to perfect every part and function in the engine. You can now put computers or even tiny crystals right into an engine.

"[It] can monitor in real time what's happening inside the cylinder, and [communicate] this to a mathematical formula, that ... says, 'Now I want you to be a little bit to the left, a little bit to the right, when it comes to [picking] the pressure.' " Stefanopoulou explains.

The Fuel Cost Of 'Creature Comforts'

The researchers don't just work on engines but also with how drivers perceive the driving, with the help of psychologists and statisticians. Stefanopoulou and her colleagues say the barriers to getting to 55 mpg aren't scientific.

"When we talk about 55 mpg, we had that technology, criminy, 20 years ago," says Margaret Wooldridge, who's also a professor at the University of Michigan in the Department of Mechanical Engineering. She says there's a but — in this case, the car driver.

"Like when was the last time you actually took your hand and rolled down a window?" she asks. "But now there's an expectation that every vehicle, even if it's an entry-level vehicle, will have that kind of creature comfort [power windows]."

Wooldridge says we expect our cars to heat faster in winter, to cool faster in summer, have seat warmers and be able to plug in two cell phones, maybe a DVD player and — of course — a radio.

"I personally owned a vehicle that had over 45 mpg fuel economy when I was in college," Wooldridge says. "And it had a manual transmission, manual windows; it was a great car, [it] lasted forever. It was light-weight, kind of chilly to heat in the winter and all that good stuff."

Wooldridge says all those extras can reduce the fuel economy by up to 50 percent — and that it's a fat chance people are going to give up plugging in their cell phones or running the air conditioner or cranking NPR.

"Expecting people to make good choices at a cost premium isn't going to work," she says. "So if we're trying to effect positive change, if we're trying to change behaviors and change emissions and things like that, you're not going to get people to do that unless you can do it cost competitively."

Wooldridge says there are many regular inexpensive gas-powered cars that get more than 40 miles a gallon. The real race is to do that with all kinds of cars, from the showy luxury cars to economy cars.

"You need it all, you have to have it all," she says. "You're not going to get there exclusively on one engine technology or one powertrain technology. You need to have a variety of powertrain technologies. So hybrids have a role to play, they absolutely do. Electric vehicles have a role to play."

Wooldridge says that regular gas engines are going to be on the road for quite some time to come, and that the science exists to make cars vastly more fuel efficient.

The limits, she says, are cost and our desire to get there.

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